When you travel overnight for work, you're entitled to claim the per diem meal rate for the place you spent the night. You count how many nights you were there and multiply it by the per diem "meals and incidentals rate" for that county (or foreign province).

Since the IRS sets the per diem rate, as long as they accept that it was a qualified business trip, they will accept the per diem expenses, even if it's not what you actually spent on meals during your trip.

You can look up the per diem meal rate at www.perdiem101.com